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A307758
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Average of twin prime pairs that is a product of two averages of twin prime pairs.
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2
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72, 108, 180, 240, 432, 600, 828, 1152, 1620, 1872, 2088, 2592, 3528, 3852, 4128, 4932, 4968, 5280, 6300, 6552, 6792, 7488, 7560, 9000, 9240, 9720, 10008, 10332, 11160, 11700, 12240, 13008, 13680, 15288, 16632, 18540, 20232, 20772, 20808, 21492, 25308, 25800, 26892
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OFFSET
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1,1
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COMMENTS
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All terms == 0, 24, 36 or 48 (mod 72). - Robert Israel, Apr 30 2019
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LINKS
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EXAMPLE
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108 = 6*18. 6 and 18 are both averages of twin prime pairs, so 108 is in the sequence.
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MAPLE
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N:= 10^5: # to get all terms <= N
P:= select(isprime, {seq(i, i=3..N+1, 2)}):
TPA:= map(`+`, P, 1) intersect map(`-`, P, 1):
R:= select(t -> ormap(d -> member(t/d, TPA), TPA intersect numtheory:-divisors(t)), TPA):
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PROG
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(PARI) isok1(n) = isprime(n-1) && isprime(n + 1);
isok2(n) = fordiv(n, d, if (isok1(d) && isok1(n/d), return(1)); );
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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